I remember James Marsters saying in an interview once that Sarah was the only person he had ever met who worked harder at perfecting her role than he did. Add that to the fact that she was in almost every scene of every episode of all 7 seasons. Add to that, she was also in almost every single fight scene in every episode, which required physical training and studying the choreography for each and every one of those fights, and you wind up with a pretty tired little girl by the time that the day is over. Also, she was probably lucky to average 5 hours' sleep a night at best. The other actors had far more down time than she did, so it only makes sense that they would do the interviews and give her the chance to catch what rest that she could, and, hopefully, wolf down at least a minimal amount of nourishment.
